kernel: Add locking to BinaryFormat and DeviceRegistry

This resulted in very weird backtraces.

kernel/CMakeLists.txt

@@ -56,6 +56,8 @@ set(SOURCES
     src/fs/MBR.cpp
     src/fs/GPT.cpp
     src/fs/StorageCache.cpp
+    src/fs/OpenFileDescription.cpp
+    src/fs/FSRegistry.cpp
     src/net/UnixSocket.cpp
     src/fs/tmpfs/FileSystem.cpp
     src/fs/tmpfs/Inode.cpp
@@ -118,7 +120,7 @@ target_link_libraries(moon luna-freestanding)
 target_compile_definitions(moon PRIVATE IN_MOON)
 
 target_compile_options(moon PRIVATE ${COMMON_FLAGS})
-target_compile_options(moon PRIVATE -nostdlib -mcmodel=kernel -ffreestanding)
+target_compile_options(moon PRIVATE -nostdlib -mcmodel=kernel -ffreestanding -fno-threadsafe-statics)
 
 if("${LUNA_ARCH}" MATCHES "x86_64")
     target_compile_options(moon PRIVATE -mno-red-zone)

kernel/src/Symbols.cpp

@@ -3,6 +3,7 @@
 #include "arch/MMU.h"
 #include "boot/bootboot.h"
 #include "fs/InitRD.h"
+#include "lib/Mutex.h"
 #include <luna/Scanf.h>
 #include <luna/TarStream.h>
 #include <luna/Vector.h>
@@ -18,6 +19,7 @@ struct Symbol
 };
 
 Vector<Symbol> g_symbols;
+static Mutex g_lock;
 
 extern const u8 kernel_start;
 extern const u8 kernel_end;
@@ -38,6 +40,8 @@ namespace Symbols
 {
     Result<void> load()
     {
+        ScopedMutexLock lock(g_lock);
+
         const u64 virtual_initrd_address = MMU::translate_physical_address(bootboot.initrd_ptr);
 
         TarStream stream;
@@ -80,14 +84,11 @@ namespace Symbols
         if (address < (u64)&kernel_start) return StringView {};
         if (address >= (u64)&kernel_end) return StringView {};
 
+        ScopedMutexLock lock(g_lock);
+
         for (isize i = (isize)g_symbols.size() - 1; i >= 0; i--)
         {
-            if (g_symbols[i].address < address)
-            {
-                usize index = i + 1;
-                if (index == g_symbols.size()) return StringView {};
-                return StringView { g_symbols[index].symbol };
-            }
+            if (g_symbols[i].address < address) { return StringView { g_symbols[i].symbol }; }
         }
 
         return StringView {};

kernel/src/binfmt/BinaryFormat.cpp

@@ -1,6 +1,7 @@
 #include "binfmt/BinaryFormat.h"
 #include "binfmt/ELF.h"
 #include "binfmt/Script.h"
+#include "lib/Mutex.h"
 
 struct BinaryFormatDescriptor
 {
@@ -10,6 +11,8 @@ struct BinaryFormatDescriptor
 
 Vector<BinaryFormatDescriptor> g_binary_formats;
 
+static Mutex g_lock;
+
 Result<void> BinaryFormat::init()
 {
     TRY(register_binary_format(ELFLoader::create, nullptr));
@@ -20,6 +23,7 @@ Result<void> BinaryFormat::init()
 
 Result<void> BinaryFormat::register_binary_format(binfmt_loader_creator_t creator, void* arg)
 {
+    ScopedMutexLock lock(g_lock);
     return g_binary_formats.try_append({ creator, arg });
 }
 
@@ -27,6 +31,8 @@ Result<SharedPtr<BinaryFormatLoader>> BinaryFormat::create_loader(SharedPtr<VFS:
 {
     if (recursion_level >= 8) return err(ELOOP);
 
+    ScopedMutexLock lock(g_lock);
+
     for (const auto& format : g_binary_formats)
     {
         auto loader = TRY(format.creator(inode, format.arg, recursion_level));

kernel/src/fs/FSRegistry.cpp

@@ -0,0 +1,96 @@
+/**
+ * @file FSRegistry.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Kernel registry of available file system implementations.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include "fs/FSRegistry.h"
+#include "fs/devpts/FileSystem.h"
+#include "fs/ext2/FileSystem.h"
+#include "fs/tmpfs/FileSystem.h"
+#include "lib/Mutex.h"
+
+struct VirtualFileSystemDescriptor
+{
+    StringView name;
+    VirtualFileSystemFactoryFunction factory_function;
+};
+
+struct PhysicalFileSystemDescriptor
+{
+    StringView name;
+    PhysicalFileSystemFactoryFunction factory_function;
+};
+
+Vector<VirtualFileSystemDescriptor> g_virtual_filesystems;
+Vector<PhysicalFileSystemDescriptor> g_physical_filesystems;
+
+static Mutex g_lock;
+
+namespace FSRegistry
+{
+    Result<void> init()
+    {
+        TRY(register_virtual_filesystem(TmpFS::FileSystem::create, "tmpfs"));
+        TRY(register_virtual_filesystem(DevPTS::FileSystem::create, "devpts"));
+        TRY(register_virtual_filesystem(DeviceRegistry::create_devfs_instance, "devfs"));
+        TRY(register_physical_filesystem(Ext2::FileSystem::create, "ext2"));
+
+        return {};
+    }
+
+    Result<void> register_virtual_filesystem(VirtualFileSystemFactoryFunction factory_function, StringView name)
+    {
+        ScopedMutexLock lock(g_lock);
+
+        for (const auto& descriptor : g_virtual_filesystems)
+        {
+            if (descriptor.name == name) return err(EEXIST);
+        }
+
+        auto descriptor = VirtualFileSystemDescriptor { .name = name, .factory_function = factory_function };
+
+        return g_virtual_filesystems.try_append(move(descriptor));
+    }
+
+    Result<void> register_physical_filesystem(PhysicalFileSystemFactoryFunction factory_function, StringView name)
+    {
+        ScopedMutexLock lock(g_lock);
+
+        for (const auto& descriptor : g_physical_filesystems)
+        {
+            if (descriptor.name == name) return err(EEXIST);
+        }
+
+        auto descriptor = PhysicalFileSystemDescriptor { .name = name, .factory_function = factory_function };
+
+        return g_physical_filesystems.try_append(move(descriptor));
+    }
+
+    Result<VirtualFileSystemFactoryFunction> lookup_virtual_filesystem(StringView name)
+    {
+        ScopedMutexLock lock(g_lock);
+
+        for (const auto& descriptor : g_virtual_filesystems)
+        {
+            if (descriptor.name == name) return descriptor.factory_function;
+        }
+
+        return err(ENODEV);
+    }
+
+    Result<PhysicalFileSystemFactoryFunction> lookup_physical_filesystem(StringView name)
+    {
+        ScopedMutexLock lock(g_lock);
+
+        for (const auto& descriptor : g_physical_filesystems)
+        {
+            if (descriptor.name == name) return descriptor.factory_function;
+        }
+
+        return err(ENODEV);
+    }
+}

kernel/src/fs/FSRegistry.h

@@ -0,0 +1,62 @@
+/**
+ * @file FSRegistry.h
+ * @author apio (cloudapio.eu)
+ * @brief Kernel registry of available file system implementations.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include "fs/VFS.h"
+#include "fs/devices/Device.h"
+
+typedef Result<SharedPtr<VFS::FileSystem>> (*VirtualFileSystemFactoryFunction)(void);
+typedef Result<SharedPtr<VFS::FileSystem>> (*PhysicalFileSystemFactoryFunction)(SharedPtr<Device>);
+
+namespace FSRegistry
+{
+    /**
+     * @brief Register the built-in file system implementations.
+     *
+     * @return Result<void> Whether the operation succeeded.
+     */
+    Result<void> init();
+
+    /**
+     * @brief Register a "virtual" (in-memory) file system implementation, associating a name to it.
+     *
+     * @param factory_function The factory function to use to create new instances of this file system.
+     * @param name The name to associate with this file system implementation.
+     * @return Result<void> Whether the operation succeeded.
+     */
+    Result<void> register_virtual_filesystem(VirtualFileSystemFactoryFunction factory_function, StringView name);
+
+    /**
+     * @brief Register a "physical" (mounted from a device) file system implementation, associating a name
+     * to it.
+     *
+     * @param factory_function The factory function to use to create new instances of this file system.
+     * @param name The name to associate with this file system implementation.
+     * @return Result<void> Whether the operation succeeded.
+     */
+    Result<void> register_physical_filesystem(PhysicalFileSystemFactoryFunction factory_function, StringView name);
+
+    /**
+     * @brief Find a "virtual" (in-memory) file system implementation by name.
+     *
+     * @param name The name to look for.
+     * @return Result<VirtualFileSystemFactoryFunction> An error, or the factory function to create file systems of this
+     * type.
+     */
+    Result<VirtualFileSystemFactoryFunction> lookup_virtual_filesystem(StringView name);
+
+    /**
+     * @brief Find a "physical" (mounted from a device) file system implementation by name.
+     *
+     * @param name The name to look for.
+     * @return Result<PhysicalFileSystemFactoryFunction> An error, or the factory function to create file systems of
+     * this type.
+     */
+    Result<PhysicalFileSystemFactoryFunction> lookup_physical_filesystem(StringView name);
+}

kernel/src/fs/OpenFileDescription.cpp

@@ -0,0 +1,33 @@
+#include "fs/OpenFileDescription.h"
+#include <bits/open-flags.h>
+
+OpenFileDescription::OpenFileDescription(SharedPtr<VFS::Inode> ino, int fl) : inode(ino), flags(fl)
+{
+    inode->add_handle();
+}
+
+OpenFileDescription::~OpenFileDescription()
+{
+    inode->remove_handle();
+    inode->did_close();
+}
+
+bool FileDescriptor::should_append()
+{
+    return description->flags & O_APPEND;
+}
+
+bool FileDescriptor::should_block()
+{
+    return !(description->flags & O_NONBLOCK);
+}
+
+bool FileDescriptor::is_readable()
+{
+    return description->flags & O_RDONLY;
+}
+
+bool FileDescriptor::is_writable()
+{
+    return description->flags & O_WRONLY;
+}

kernel/src/fs/OpenFileDescription.h

@@ -0,0 +1,36 @@
+#pragma once
+#include "fs/VFS.h"
+#include <luna/SharedPtr.h>
+#include <luna/String.h>
+
+struct OpenFileDescription : public Shareable
+{
+    SharedPtr<VFS::Inode> inode;
+    int flags { 0 };
+    String path;
+
+    OpenFileDescription(SharedPtr<VFS::Inode>, int);
+    ~OpenFileDescription();
+};
+
+struct FileDescriptor
+{
+    SharedPtr<OpenFileDescription> description;
+    usize offset { 0 };
+    int flags { 0 };
+
+    bool should_append();
+    bool should_block();
+    bool is_writable();
+    bool is_readable();
+
+    SharedPtr<VFS::Inode> inode()
+    {
+        return description->inode;
+    }
+
+    int& status_flags()
+    {
+        return description->flags;
+    }
+};

kernel/src/fs/devices/DeviceRegistry.cpp

@@ -12,6 +12,7 @@
 #include "fs/devices/UARTDevice.h"
 #include "fs/devices/ZeroDevice.h"
 #include "fs/tmpfs/FileSystem.h"
+#include "lib/Mutex.h"
 #include "thread/Thread.h"
 #include <luna/Vector.h>
 
@@ -26,10 +27,14 @@ struct DeviceDescriptor
 
 Vector<DeviceDescriptor> g_available_devices = {};
 
+static Mutex g_lock;
+
 namespace DeviceRegistry
 {
     Result<SharedPtr<Device>> fetch_special_device(u32 major, u32 minor)
     {
+        ScopedMutexLock lock(g_lock);
+
         for (const auto& descriptor : g_available_devices)
         {
             if (descriptor.major == major && descriptor.minor == minor) return descriptor.device;
@@ -38,7 +43,7 @@ namespace DeviceRegistry
         return err(ENODEV);
     }
 
-    Result<void> create_special_device_inode(SharedPtr<VFS::FileSystem> fs, const DeviceDescriptor& descriptor)
+    static Result<void> create_special_device_inode(SharedPtr<VFS::FileSystem> fs, const DeviceDescriptor& descriptor)
     {
         auto inode = TRY(fs->create_device_inode(descriptor.major, descriptor.minor, descriptor.mode));
         TRY(fs->root_inode()->add_entry(inode, descriptor.name));
@@ -48,6 +53,8 @@ namespace DeviceRegistry
 
     Result<void> register_special_device(u32 major, u32 minor, SharedPtr<Device> device, mode_t mode)
     {
+        ScopedMutexLock lock(g_lock);
+
         for (const auto& descriptor : g_available_devices)
         {
             if (descriptor.major == major && descriptor.minor == minor) return err(EEXIST);
@@ -82,7 +89,7 @@ namespace DeviceRegistry
 
     dev_t next_null_device_id()
     {
-        static u32 next_minor = 0;
+        static Atomic<u32> next_minor = 0;
         return luna_dev_makedev(0, next_minor++);
     }
 

kernel/src/main.cpp

@@ -5,6 +5,7 @@
 #include "binfmt/BinaryFormat.h"
 #include "boot/Init.h"
 #include "config.h"
+#include "fs/FSRegistry.h"
 #include "fs/InitRD.h"
 #include "fs/devices/DeviceRegistry.h"
 #include "fs/devices/PTYMultiplexer.h"
@@ -62,6 +63,7 @@ void oom_thread()
         mark_critical(DeviceRegistry::init(), "Failed to register initial devices");
 
         mark_critical(BinaryFormat::init(), "Failed to register initial binary formats");
+        mark_critical(FSRegistry::init(), "Failed to register initial file systems");
 
         auto init =
             mark_critical(VFS::resolve_path("/bin/preinit", Credentials {}), "Can't find init in the initial ramfs!");

kernel/src/sys/mount.cpp

@@ -1,4 +1,5 @@
 #include "Pledge.h"
+#include "fs/FSRegistry.h"
 #include "fs/VFS.h"
 #include "fs/devpts/FileSystem.h"
 #include "fs/ext2/FileSystem.h"
@@ -26,18 +27,18 @@ Result<u64> sys_mount(Registers*, SyscallArgs args)
 
     SharedPtr<VFS::FileSystem> fs;
 
-    if (fstype.view() == "tmpfs") fs = TRY(TmpFS::FileSystem::create());
-    else if (fstype.view() == "devpts")
-        fs = TRY(DevPTS::FileSystem::create());
-    else if (fstype.view() == "devfs")
-        fs = TRY(DeviceRegistry::create_devfs_instance());
-    else if (fstype.view() == "ext2")
+    auto maybe_virtual = FSRegistry::lookup_virtual_filesystem(fstype.view());
+    if (maybe_virtual.has_value())
     {
-        auto source_device = TRY(get_source());
-        fs = TRY(Ext2::FileSystem::create(source_device));
+        auto factory = maybe_virtual.release_value();
+        fs = TRY(factory());
     }
     else
-        return err(ENODEV);
+    {
+        auto factory = TRY(FSRegistry::lookup_physical_filesystem(fstype.view()));
+        auto device = TRY(get_source());
+        fs = TRY(factory(device));
+    }
 
     TRY(VFS::mount(target.chars(), fs, current->auth, current->current_directory));
 

kernel/src/thread/Thread.cpp

@@ -236,34 +236,3 @@ void Thread::send_signal(int signo)
         wake_up();
     }
 }
-
-OpenFileDescription::OpenFileDescription(SharedPtr<VFS::Inode> ino, int fl) : inode(ino), flags(fl)
-{
-    inode->add_handle();
-}
-
-OpenFileDescription::~OpenFileDescription()
-{
-    inode->remove_handle();
-    inode->did_close();
-}
-
-bool FileDescriptor::should_append()
-{
-    return description->flags & O_APPEND;
-}
-
-bool FileDescriptor::should_block()
-{
-    return !(description->flags & O_NONBLOCK);
-}
-
-bool FileDescriptor::is_readable()
-{
-    return description->flags & O_RDONLY;
-}
-
-bool FileDescriptor::is_writable()
-{
-    return description->flags & O_WRONLY;
-}

kernel/src/thread/Thread.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "arch/MMU.h"
+#include "fs/OpenFileDescription.h"
 #include "fs/VFS.h"
 #include "memory/AddressSpace.h"
 #include <bits/signal.h>
@@ -29,37 +30,6 @@ enum class ThreadState
     Dying
 };
 
-struct OpenFileDescription : public Shareable
-{
-    SharedPtr<VFS::Inode> inode;
-    int flags { 0 };
-
-    OpenFileDescription(SharedPtr<VFS::Inode>, int);
-    ~OpenFileDescription();
-};
-
-struct FileDescriptor
-{
-    SharedPtr<OpenFileDescription> description;
-    usize offset { 0 };
-    int flags { 0 };
-
-    bool should_append();
-    bool should_block();
-    bool is_writable();
-    bool is_readable();
-
-    SharedPtr<VFS::Inode> inode()
-    {
-        return description->inode;
-    }
-
-    int& status_flags()
-    {
-        return description->flags;
-    }
-};
-
 static constexpr int FD_MAX = 64;
 
 struct Credentials